What about your budget ?
the best is 1080TI but 1070 is also good.
Red 56th vegas also great
For small budget for now good modded RX550 cards for mining cryptonight and eth forks
i have a large budget and want to get the best possible cards ,i just love the mining aspect of crytpo any end profit is a bonus
Then what about wait and buy new ASIC F3 on GDDR3 memory, if you love only GPU mining rigs then create from 1080TI and VEGA 56/64